1. Field of the Invention
The present invention relates to a reciprocating compressor, and more particularly, to a reciprocating motor that a winding coil is wound at an inner stator and a reciprocating compressor having the same.
2. Description of the Conventional Art
FIG. 1 is a section view showing a reciprocating compressor in accordance with the conventional art.
The conventional reciprocating compressor comprises: a hermetic casing 106; a reciprocating motor 108 installed in the casing 106 and generating a reciprocation force; and a compression unit 110 for compressing a fluid by receiving a reciprocation force from the reciprocating motor 108.
A suction pipe 102 for sucking a fluid and a discharge pipe 104 for discharging a compressed fluid are respectively connected to the casing 106, and frames 112, 114 and 116 for supporting the compression unit 110 and the reciprocating motor 108 are mounted in the casing 106.
The frames are composed of a first frame 112 for supporting a front side of the reciprocating motor 108; a second frame 114 coupled to the first frame 112 and supporting a rear side of the reciprocating motor 108; and a third frame 116 coupled to the second frame 114 and supporting a resonance spring 136.
As shown in FIG. 2, the reciprocating motor 108 is composed of: an outer stator 120 fixed between the first frame 112 and the second frame 114; an inner stator 122 arranged with a certain air gap from an inner circumferential surface of the outer stator 120; a winding coil 124 arranged at the inner circumferential surface of the outer stator 120 and to which an external power is applied; and a magnet 126 arranged between the outer stator 120 and the inner stator 122 with a certain interval and linearly-reciprocated when a power is applied to the winding coil 124.
The outer stator 120 is formed accordingly as core blocks that a plurality of lamination sheets are laminated are arranged with the same interval in a circumferential direction thereof. A bobbin 128 is fixed to an inner side surface of the core blocks, and the winding coil 124 is wound on the bobbin 128.
The inner stator 122 has a cylindrical shape that a plurality of lamination sheets are laminated, and is fixed to an outer circumferential surface of a cylinder 130 of the compression unit 110.
The magnet 126 is fixed to an outer circumferential surface of a magnet frame 132 with the same interval, and the magnet frame 132 is connected to a piston 140 of the compression unit 110. Also, a spring supporting bar 142 is connected to the piston 140. As the magnet 126, an NdFeB based magnet having a high coercive force is used.
A first resonance spring 134 is installed between the spring supporting bar 142 and the second frame 114 for supporting the outer stator 120, and the second resonance spring 136 is installed between the spring supporting bar 142 and the third frame 116 thereby to induce a resonant motion of the piston 140.
The compression unit 110 is composed of: the piston 140 connected to the magnet frame 126 thus to be linearly-moved; the cylinder 130 to which the piston 140 is slidably inserted, having a compression chamber 143, and fixed to the first frame 112; a suction valve 146 mounted at a front side of the piston 140, for opening and closing a fluid passage 144 formed at the piston 140; and a discharge valve assembly mounted at a front side of the cylinder 130, for discharging a fluid by opening the compression chamber 143 when a pressure inside the compression chamber 143 reaches a certain level.
The discharge valve assembly is composed of: a discharge valve 148 adhered to a front surface of the cylinder 130 thus to be opened and closed; a discharge cover 150 mounted at a front side of the cylinder 130 and connected to the discharge pipe 104; and a spring 152 installed between an inner surface of the discharge cover 150 and the discharge valve 148, for elastically supporting the discharge valve 148.
An operation of the conventional reciprocating compressor will be explained as follows.
When the electric power is applied to the winding coil 124, a flux is formed around the winding coil 124. The flux forms a closed loop along with the outer stator 120 and the inner stator 122. By an interaction between the flux formed between the outer stator 120 and the inner stator 122 and a flux formed by the magnet 126, the magnet 126 is linearly-moved in an axial direction. When a direction of a current applied to the winding coil 124 is alternately changed, a direction of the flux of the winding coil 124 is changed and thereby the magnet 126 is linearly-reciprocated.
As the magnet 126 is moved, the magnet frame 132 to which the magnet 126 is fixed is linearly-reciprocated thereby to linearly-reciprocate the piston 140. According to this, a fluid sucked through the suction pipe 102 is introduced into the compression chamber 143 through the fluid passage 144 of the piston 140, and the fluid that has been introduced into the compression chamber 143 is compressed by the reciprocation of the piston 140 and is discharged to the outside through the discharge pipe 104.
However, the conventional reciprocating compressor has the following problems. First, since the expensive NdFeB based magnet is used as a magnet, the winding coil is arranged at the outer stator in order to reduce a usage amount of the magnet. However, arranging the winding coil at the outer stator causes the winding coil to be unnecessarily much used thereby to increase a fabrication cost.
Also, since the winding coil is arranged on the outer stator, the number of windings of the coil is increased. According to this, a resistance of the coil is increased thereby to cause a loss of the motor.